The present invention relates to a film processor, particularly to an apparatus to control the agitation of the developer adequately and minimize deterioration of the developer caused by oxidation.
The most popular type of film processor, continuous feed type, has generally been so composed that film inserted from one end of a processor is subjected to all the required processings such as developing, fixing, washing and drying, and processed film is discharged from the other end of the processor. In all the required processings, the developing is most important and requires careful operations. That is, four factors, i.e. developing time, temperature of developer, agitation of the developer and activity of the developer, have influence primarily upon the processing completion. Many of the processors are so composed that the factors are respectively controlled to a predetermined value which is set in advance.
As for the agitation of the developer among the above four factors, attention should be paid to following two aspects: the ratio of the agitating time to the whole developing time and the intensity of the agitation. Ordinarily a pump is provided outside a developing tank to circulate or agitate the developer, in which the rate of the pump rotation is kept at a predetermined level. Since the developer is agitated in such a manner as mentioned above, comparatively fresh developer is supplied even to highly exposed parts of film to enable prompt development and accordingly to ensure fine development. The more the agitation of the developer, the higher the effect of evenness, efficiency and prompt operation. On the other hand, however, the high degree of the agitation promotes oxidation and acclerates deterioration of the developer. Consequently, it is considered favorable to continuously agitate the developer while film is supplied in the developing tank and subject to the developing treatment, and to suspend the agitation when no film is supplied in it. In which it should be taken into consideration that the developer is deteriorated due to consumption of the developing solution, by-product of development or oxidation caused by the agitation. In order to compensate for the developer deterioration, it is required to replenish fresh developer and/or to control the composition of the developer evenly at all the parts.
Conventionally the developing tank has been made deeper to minimize the surface of the developer which is exposed with air, in which the developer agitation is not suspended even after developing. This arrangement, however, has not been effective enough. Or, in order to prevent the developer from deteriorating, a film processor which is so composed that both the agitation degree of the developer and the film conveyance through the developer can be varied in accordance with the film position has been made. This arrangement, however, makes a film processor itself large sized and is very expensive.